1-C PU adhesives are known. DE 23 65 623 describes a liquid polyfunctional polisocyanate precondensate with an NCO content of 2 to 15% by weight for bonding wet wood. Additives such as, for example, dyes, solvent, water and foam control agents may be added to the PU precondensate. Above all, fillers may also be added to improve processability, for example to increase viscosity, to impart thixotropic properties, to prevent penetration into the wood, to increase provisional adhesion during prepressing and the like. The many fillers actually mentioned include inter alia colloidal silicon dioxide and silica gel powder. Wood meal above all is used in the Examples. Although 15 to 25% by weight of such fillers are added, the adhesives are liquid and tend to drip, albeit to a lesser extent than without the added filler (see page 15, bottom).
From this emerges the problem addressed by the present invention, namely to provide a 1-C PU adhesive with such particular rheological properties that, on the one hand, it would be sufficiently flowable to be expressed from pressurized containers or cartridges, for example, but on the other hand would show satisfactory creep resistance and would not drip or flow down vertical surfaces. The adhesive properties typical of a structural and assembly adhesive would of course remain intact.